Editorial: Special issue on WeB 2006

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Organizational mechanisms for enhancing user innovation in information technology

MIS Quarterly: Management Information Systems233365-395MISQ

On the parameters of Johnson-Mehl-Avrami-Kolmogorov equation for the hydride growth mechanisms: A case of MgH2

Kinetic parameter (k) and growth dimensionality (n) of Johnson-Mehl-Avrami-Kolmogorov equation are sensitive to phenomena controlling magnesium hydrogenation (210 degrees C, P-H2 = 1 MPa). Interfacial movement followed by H-atom diffusion through hydride controls hydride growth. During interfacial growth, k varies negligibly unlike n(> 0.50). Interfacial-to-diffusional transition is characterized by significantly varying k and negligibly varying n(< 0.50). Diffusional growth renders k and n(< 0.50) almost constant. Combined k - n analysis, supported by other kinetic and geometric parameters, can identify hydride growth mechanisms. (c) 2017 Published by Elsevier B.V

Transition from interfacial to diffusional growth during hydrogenation of Mg

The transition from interfacial to diffusional growth during hydrogenation of Mg -> MgH2 (hydride) at 210 degrees C for 300 min is studied using Johnson-Mehl-Avrami-Kolmogorov equation (alpha = 1 - exp(- kt(n))). The growth dimensionality (n) decreases from 0.73 to 0.23. 1D (hydride/metal) interfacial growth occurs when n > 0.50, suggested by constant interface velocity (U). Diffusional growth at n <0.50 is confirmed by the core-shell (Mg-MgH2) structure, drop in U by similar to 2-orders and the diffusion coefficient (D) of H-atom through hydride. The transition from 1D interfacial to diffusional growth occurs at n approximate to 0.50. (C) 2015 Elsevier B.V. All rights reserved

Contributions of multiple phenomena towards hydrogenation: A case of Mg

Heterogeneous hydrogenation involves chemisorption (Chem), nucleation and growth by interfacial movement (NG) and diffusion (Diff). The slowest one of these phenomena is generally considered to control hydrogenation. However, the considered phenomenon cannot explain the hydrogenation in its entirety. Multiple phenomena can contribute to different extents towards hydrogenation. Contributions of multiple phenomena are explained by developing functions of the form xi(t) = Pi(i = Chem, NG, Diff) (j = Chem,) (i not equal j) f(j) (t)center dot(xi(ai(t))(i). xi(t) is the converted fraction of hydride. The indices a(i)(t) represent the extents to which the explicitly considered phenomena act (represented by xi(i)(t) from literature). Constraints Sigma(i)a(i)(t)6 = 1 and the condition f(j)(t)-> 1 ascertain the exhaustiveness of the phenomena considered. Mg-MgH2 is considered as a proof-of-concept system to apply the present approach. The (t) functions are applied to describe the hydrogenation behaviour of Mg (similar to 44 mu m) at 210 degrees C and P-H2 = 1 MPa. Present analysis shows that multiple phenomena can act simultaneously and the dominant one (highest value of index) controls the hydrogenation. This dominant phenomenon can change with time such that chemisorption followed by NG and finally diffusion contribute in controlling hydrogenation. The estimated activation energies for NG (42 kJ/mol H) and diffusion (97 kJ/mol H) compare well with literature. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved